Liquid treatment apparatus

Abstract

The disclosure relates to a liquid treatment apparatus which includes a clarifier tank and an integral sludge thickener tank. Liquid enters the clarifier tank through an inlet member disposed generally centrally of the bottom wall of the member and passes upwardly through an eductor member into a mixing zone defined by a reaction cone. Recirculation of liquid and suspended particles below the cone promotes flocculation of those particles. Gravity settling also takes place in the relatively quiescent area outside the cone. The liquid inlet member is of divergent cross-sectional shape for dissipating some of the energy in the liquid and a variable speed rotary impeller is disposed in the inlet and can be adjusted to control liquid circulation according to the flow rate of influent liquid. The apparatus also includes an integral sludge thickener tank to which sludge and liquid are continuously delivered from the clarifier tank. Clarified water from the thickener is returned to the clarifier tank and the effluent from the thickener tank is discarded.

I claim: 
     
       1. Liquid treatment apparatus comprising: a clarifier tank for containing a body of liquid extending to a predetermined liquid level in the tank;   an inlet for liquid containing suspended particles;   liquid outlet means disposed generally at said predetermined liquid level and through which clarified liquid can leave the tank;   means in said tank for promoting settling of said particles from said liquid;   a sump in a bottom wall of said tank for receiving settled particles in the form of a sludge;   sludge conveyor means operable to convey settled particles towards said sump;   a thickener tank closely associated with said clarifier tank and having a clarified liquid outlet adjacent an upper end of the tank, a sludge outlet adjacent a lower end of the tank through which settled sludge can be periodically removed from the apparatus, and an inlet intermediate said outlets, said inlet and outlets being below said predetermined liquid level in the clarifier tank;   a conduit extending from said clarifier tank sump to said thickener tank inlet, whereby the head of liquid in the clarifier tank above the sump causes sludge and liquid to continuously flow from said sump into said thickener tank, and causes clarified liquid to flow continuously from said thickener tank liquid outlet;   means in said thickener tank for promoting thickening of particles in liquid in the tank; and,   means coupling said clarified liquid outlet of the thickener tank into one of said inlet and liquid outlet means of the clarifier tank.   
     
     
       2. Liquid treatment apparatus comprising: a tank for containing a body of liquid;   a liquid inlet conduit through which liquid containing suspended particles can be delivered to the tank;   liquid outlet means disposed generally at the level of the surface of said body of liquid and through which clarified liquid can leave the tank;   sludge outlet means comprising a sump in a bottom wall of the tank for receiving settled particles and from which said particles can be removed as a sludge;   sludge conveyor means operable to convey settled particles towards said sludge outlet means;   a thickener tank closely associated with the first-mentioned tank and having a clarified liquid outlet adjacent its upper end, a sludge outlet adjacent its lower end through which settled sludge can be periodically removed from the apparatus, and an inlet intermediate said outlets, said inlets and outlets being below said level of the surface of the body of liquid in the first-mentioned tank;   a conduit extending from said sump to said thickener tank inlet, whereby the head of liquid above said sump causes sludge and liquid to continuously flow from said sump into said thickener tank, and causes clarified liquid to flow continuously from said thickener tank liquid outlets; and,   means in said thickener tank for promoting thickening of particles in liquid in the tank;   an inlet member disposed at an inner end of said liquid inlet conduit adjacent said bottom wall of the tank and arranged to direct influent liquid generally vertically upwards in the tank, said inlet member including generally co-axial inner and outer portions each of tubular form extending about a common axis and through which the liquid flows from end to end, said outer portion being of significantly greater cross-sectional area than said inner portion and defining a discharge end of said inlet, whereby some of the energy in liquid flowing through said inlet member is dissipated as the liquid flows from said inner end portion to said outer end portion;   static mixer means disposed in said inner portion of the inlet member;   feed means adapted to permit introduction of chemical additives into influent liquid immediately upstream of said static mixer;   a generally conical partition member disposed in the tank above said inlet and defining a circulation zone below said member, the remainder of the tank outside said partition member defining a relatively quiescent zone for gravity settling of suspended particles;   a tubular eductor member having open upper and lower ends and disposed in an upright position below said partition member and generally in alignment with said liquid inlet, said eductor member being arranged relative to said inlet so that liquid entering the tank from the inlet flows upwardly in said eductor member and through the open upper end of the member into said circulation zone, and liquid and suspended particles adjacent said open lower end of the eductor member are entrained by said upward flow of liquid, whereby a recirculation of liquid and suspended particles is established below said partition member for promoting flocculation of said particles;   rotary impeller means disposed adjacent said discharge end of said inlet in the path of liquid flowing through the inlet and adapted to control circulation of liquid and suspended particles in said circulation zone.   
     
     
       3. Apparatus as claimed in claim 2, wherein said rotary impeller means comprises a low-shear type impeller blade rotatable about said axis of the inlet member, a drive shaft extending upwardly through said eductor member and partition member to a level above the liquid level in the tank, and a variable speed drive means supported above said liquid level and coupled to said shaft for driving the impeller blade, whereby the speed of rotation of the blade can be adjusted according to mixing conditions required in the tank. 
     
     
       4. Apparatus as claimed in claim 3, further comprising a flow measuring device disposed in said influent liquid conduit and responsive to the flow rate of liquid in said conduit, and means coupled between said device and said mixer drive means for controlling the speed of rotation of said impeller blade according to the flow rate detected by said flow measuring device. 
     
     
       5. Apparatus as claimed in claim 2, wherein said static mixer means comprises a plurality of stationary mixer blades disposed in said inner end portion of the inlet and arranged to impart to liquid flowing therethrough, a turning action about the axis of the inlet. 
     
     
       6. Apparatus as claimed in claim 2, wherein said inner and outer portions of the inlet member are of cylindrical shape, and wherein the member further comprises an intermediate portion of part conical shape providing a smooth transition between said inner and outer portions. 
     
     
       7. Apparatus as claimed in claim 2, wherein said sump is offset from the centre of said bottom wall of the first-mentioned tank and is positioned in said wall adjacent said thickener tank. 
     
     
       8. Apparatus as claimed in claim 2, wherein said eductor member is shaped to define a throat immediately downstream of said discharge and of said inlet member, whereby the eductor member defines a venturi for entraining said liquid and suspended particles adjacent the open lower end of the eductor member. 
     
     
       9. Apparatus as claimed in claim 8, wherein said eductor member comprises an upper portion of substantially constant cross-sectional shape throughout its length, and a lower portion which is flared outwardly toward said open lower end of the member and which defines said thraot with said upper portion, and a deflection baffle disposed above said open upper end of the upper section and arranged to laterally deflect liquid leaving the eductor member. 
     
     
       10. Apparatus as claimed in claim 2, wherein said sludge conveyor means forms part of a sludge scraper assembly rotatable in the tank about a generally vertical axis containing said liquid inlet, said scraper assembly including: scraper means for sweeping over said bottom wall of the tank as said assembly rotates and adapted to convey settled particles towards said sludge outlet; drive means supported above the level of said body of liquid for rotating said scraper means; and a driving member coupled to said drive means and extending down into the tank generally along said axis; said eductor member forming part of sludge scraper assembly and being coupled to said scraper means and said driving member and further including deflector means disposed above said open upper end of the eductor member and arranged to outwardly deflect liquid leaving said member; and wherein the apparatus further comprises means for rotationally locating said scraper assembly with respect to said vertical axis. 
     
     
       11. Apparatus as claimed in claim 10, wherein said rotary impeller means comprises a low-shear type impeller blade rotatable about said axis of the inlet member, a drive shaft extending upwardly from said blade through said eductor member and partition member to a level above said liquid in the tank, and variable speed drive means disposed above said liquid level and coupled to said drive shaft, and wherein said driving member of the sludge scraper assembly is of tubular form and said mixer drive shaft extends longitudinally through said driving member from said drive means to said impeller blade. 
     
     
       12. Apparatus as claimed in claim 10, wherein said inner portion of the inlet member is of cylindrical shape, and wherein said means for rotationally locating the scraper assembly comprises bearing means turnably mounted on said inner portion at the inlet member, and bearing housing means carried by said eductor member and housing said bearing means. 
     
     
       13. An apparatus as claimed in claim 1 or 2 wherein said thickener tank is separate from said tank for containing a body of liquid. 
     
     
       14. An apparatus as claimed in claim 1 or 2 wherein said thickener tank is integral with said tank for containing a body of liquid and is formed by an integral extension of a side wall of said tank. 
     
     
       15. In a liquid treatment apparatus which includes a clarifier tank for containing a body of liquid extending to a predetermined liquid level in the tank; an inlet for liquid containing suspended particles; liquid outlet means disposed generally at said predetermined liquid level and through which clarified liquid can leave the tank; means in said tank for promoting settling of said particles from said liquid; a sump in a bottom wall of said tank for receiving settled particles in the form of a sludge; sludge conveyor means operable to convey settled particles towards said sump; the improvement comprising a thickener tank and having a clarified liquid outlet adjacent an upper end of the tank, a sludge outlet adjacent a lower end of the tank, through which settled slude can be periodically removed from the apparatus, and an inlet intermediate said outlets, said inlet and outlets being below said predetermined liquid level in the clarifier tank;   a conduit extending from said clarifier tank sump to said thickener tank inlet, whereby the head of liquid in the clarifier tank above the sump causes sludge and liquid to continuously flow from said sump into said thickener tank, and causes clarified liquid to flow continuously from said thickener tank liquid outlet;   means in said thickener tank for promoting thickening of particles in liquid in the tank; and,   means coupling said clarified liquid outlet of the thickener tank into one of said inlet and liquid outlet means of the clarifier tank.